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	<img id="logo" src="header.jpg" alt="Header Logo" title="Caffeine Buzz">
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<h2><a id="Sources">Sources</a></h2>
<p>
One common source of caffeine is the 
<a href="http://en.wikipedia.org/wiki/Coffea" title="Coffea">coffee plant</a>, 
the <a href="http://en.wikipedia.org/wiki/Coffee_bean" title="Coffee bean">beans</a> 
from which are used to produce <a href="http://en.wikipedia.org/wiki/Coffee" title="Coffee">coffee</a>. 
Caffeine content varies substantially between 
<a href="http://en.wikipedia.org/wiki/Arabica" title="Arabica">Arabica</a> and 
<a href="http://en.wikipedia.org/wiki/Robusta" title="Robusta">Robusta</a> species and 
to a lesser degree between varieties of each species.
</p>
<p>
One dose of caffeine is generally considered to be 100 mg. In theory, 
a single serving (6 fl oz / 150 ml) of drip coffee or one-half caffeine 
tablet would deliver this dose. In the real world, coffee varies considerably 
in caffeine content per serving, ranging from about 75 mg to 250 mg. 
Generally, dark roast coffee has less caffeine than lighter roasts since 
the roasting process reduces caffeine content of the bean.
</p>
<p>
<a href="http://en.wikipedia.org/wiki/Tea" title="Tea">Tea</a> is another common source of 
caffeine in many cultures. Tea contains somewhat less caffeine per serving 
than coffee, (usually about half as much, depending on the strength of the brew), 
though certain types of tea, such as Lapsang sou chong smoked teas, and oolong 
contain more caffeine.
</p>
<p>
Caffeine is also common in 
<a href="http://en.wikipedia.org/wiki/Soft_drink" title="Soft drink">soft drinks</a> such as 
<a href="http://en.wikipedia.org/wiki/Cola" title="Cola">cola</a>. Such drinks typically contain 
about 25 mg to 50 mg of caffeine per serving. Some 
"<a href="http://en.wikipedia.org/wiki/Energy_drink" title="Energy drink">energy drinks</a>" such as 
<a href="http://en.wikipedia.org/wiki/Red_Bull" title="Red Bull">Red Bull</a> contain 80 mg, while others 
offer considerably more caffeine per serving, from 100 mg to 400 mg.
</p>
<p>
<b>Mateine</b> and <b>guaranine</b> are other names for 
<strong>caffeine</strong>. The names come from 
<a href="http://en.wikipedia.org/wiki/Yerba_mat%C3%A9" title="Yerba mat&eacute;">yerba mat&eacute;</a> and 
<a href="http://en.wikipedia.org/wiki/Guarana" title="Guarana">guarana</a> respectively, 
caffeine-containing plants used for tea and other things. Many yerba mat&eacute;
enthusiasts insist that mateine is a 
<a href="http://en.wikipedia.org/wiki/Stereoisomer" title="Stereoisomer">stereoisomer</a> of caffeine 
and thus a different substance altogether. However, this is impossible; 
caffeine is an 
<a href="http://en.wikipedia.org/wiki/Chirality_%28chemistry%29" title="Chirality (chemistry)">achiral</a>
molecule with no chiral centers, and therefore has no stereoisomers. Similar 
claims are sometimes made of guaranine.
</p>

<p>
Caffeine is sometimes called <b>theine</b> when it is found in tea, 
as the caffeine in tea was once thought to be a separate compound to the 
caffeine found in coffee. But tea does contain another 
<a href="http://en.wikipedia.org/wiki/Xanthine" title="Xanthine">xanthine</a>, 
<a href="http://en.wikipedia.org/wiki/Theophylline" title="Theophylline">theophylline</a> whose 
chemical structure is 
<a href="http://en.wikipedia.org/wiki/Carbon" title="Carbon">C</a><sub>7</sub><a href="http://en.wikipedia.org/wiki/Hydrogen" title="Hydrogen">H</a><sub>8</sub><a href="http://en.wikipedia.org/wiki/Nitrogen" title="Nitrogen">N</a><sub>4</sub><a href="http://en.wikipedia.org/wiki/Oxygen" title="Oxygen">O</a><sub>2</sub> compared to caffeine's <a href="http://en.wikipedia.org/wiki/Carbon" title="Carbon">C</a><sub>8</sub><a href="http://en.wikipedia.org/wiki/Hydrogen" title="Hydrogen">H</a><sub>10</sub><a href="http://en.wikipedia.org/wiki/Nitrogen" title="Nitrogen">N</a><sub>4</sub><a href="http://en.wikipedia.org/wiki/Oxygen" title="Oxygen">O</a><sub>2</sub>. 
This is similar to the naming problem with <b>mateine</b> and <b>guaranine</b>.
</p>

<h3><a id="Coffee">Coffee</a></h3>
<p>
<i>All fluid ounces are U.S. fluid ounces.</i>
</p>
<ul>
<li><a href="http://en.wikipedia.org/wiki/Coffee" title="Coffee">Coffee</a>, brewed (drip) - 4 to 20 mg/floz (130 to 680 mg/litre) (40 to 170 mg/5 floz)</li>
<li>Coffee, decaffeinated - 0.4 to 0.6 mg/floz (13 to 20 mg/litre)</li>
<li>Coffee, instant - 4 to 12 mg/floz (130 to 400 mg/litre)</li>
<li><a href="http://en.wikipedia.org/wiki/Espresso" title="Espresso">Espresso</a> Arabica - ~40 mg/floz (1360 mg/litre)</li>
<li><a href="http://en.wikipedia.org/wiki/Espresso" title="Espresso">Espresso</a> Robusta - ~100 mg/floz (3400 mg/litre)</li>
</ul>

<p><a id="Teas_and_other_infusions"></a></p>

<h3><a href="http://en.wikipedia.org/wiki/Tea" 
       title="Tea"
       id="Teas_and_other_infusions">Teas</a> and other infusions</h3>
<ul>
<li><a href="http://en.wikipedia.org/wiki/Black_tea" title="Black tea">Black tea</a>, brewed (<a href="http://en.wikipedia.org/wiki/United_States" title="United States">USA</a>) - 2.5 to 11 mg/floz (85 to 370 mg per litre)</li>
<li>Black tea, brewed (other) - 3 to 14 mg/floz (100 to 470 mg/litre)</li>
<li>Black tea, canned iced - 2 to 3 mg/floz (70 to 100 mg/litre)</li>
<li>Black tea, instant - 3.5 mg/floz (120 mg/litre)</li>
<li><a href="http://en.wikipedia.org/wiki/Oolong" title="Oolong">Oolong</a>, 3.75 mg/floz (120 mg per litre) (12 to 55 mg per tea bag, i.e. one serving)</li>
<li><a href="http://en.wikipedia.org/wiki/Green_tea" title="Green tea">Green tea</a>, 2.5 mg/floz (85 mg/litre) (8 to 30 mg per tea bag, i.e. one serving)</li>
<li><a href="http://en.wikipedia.org/wiki/White_tea" title="White tea">White tea</a>, 2.0 mg/floz (68 mg/litre) (6 to 25 mg per tea bag, i.e. one serving)</li>
<li>Decaf, 0.5 mg/oz (17 mg/litre) (1 to 4 mg per tea bag, i.e. one serving)</li>
</ul>


<h3><a id="Tisane">Tisanes</a></h3>
<p>
<a href="http://en.wikipedia.org/wiki/Tisane" title="Tisane">Tisanes</a> (i.e. <a href="http://en.wikipedia.org/wiki/Herbal_tea" title="Herbal tea">Herbal teas</a>) - caffeine content depends on the herb, e.g. <a href="http://en.wikipedia.org/wiki/Chamomile" title="Chamomile">Chamomile</a> and <a href="http://en.wikipedia.org/wiki/Rooibos" title="Rooibos">Rooibos</a> "teas" have no caffeine while <a href="http://en.wikipedia.org/wiki/Yerba_mate" title="Yerba mate">Yerba mat&eacute;</a> and <a href="http://en.wikipedia.org/wiki/Guarana" title="Guarana">Guarana</a> do contain varying quantities. Many tea drinkers characterise herbal tea simply as that which, unlike black or green tea, contains no caffeine.
</p>

<h3><a id="Chocolate">Chocolate</a></h3>
<p><a href="http://en.wikipedia.org/wiki/Chocolate" title="Chocolate">Chocolate</a> is a weak stimulant due to to its content of theobromine, theophylline, and caffeine.<a href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&amp;db=pubmed&amp;dopt=Abstract&amp;list_uids=15549276" class='external autonumber' title="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&amp;db=pubmed&amp;dopt=Abstract&amp;list uids=15549276">[1]</a> However, chocolate contains too little of these compounds for a reasonable serving to create effects in humans that are on par with a <a href="http://en.wikipedia.org/wiki/Coffee" title="Coffee">coffee</a> buzz.</p>

<h3><a id="Other_sources">Other sources</a></h3>
<ul>
<li><a href="http://en.wikipedia.org/wiki/Energy_drink" title="Energy drink">Energy drink</a> - 10 mg/floz (340 mg/litre). Some countries limit the caffeine content at 135 mg/litre.</li>
<li><a href="http://en.wikipedia.org/wiki/Soft_drink" title="Soft drink">Soft drink</a> (caffeinated) - 3 to 8 mg/floz (100 to 270 mg/litre, some countries limit the caffeine content in cola drinks to 200 mg/l)</li>
<li>Pill (caffeine) - 200 mg (100 mg in Canada and many countries within EU)</li>
<li><a href="http://en.wikipedia.org/wiki/Buckfast_Tonic_Wine" title="Buckfast Tonic Wine">Buckfast Tonic Wine</a> - 0.05% of caffeine by weight<a href="http://www.young.shaney.freewebspace.com/images/buckfast.jpg" class='external autonumber' title="http://www.young.shaney.freewebspace.com/images/buckfast.jpg">[2]</a></li>
</ul>

<h3><a id="Equivalents_to_200_mg_of_caffeine">Equivalents to 200 mg of caffeine</a></h3>
<ul>
<li>One caffeine pill (Two in some countries where these are 100 mg)</li>
<li>~2 shots of espresso from robusta beans (2 floz)</li>
<li>~5 shots of espresso from arabica beans (5 floz)</li>
<li>~2 "5 floz containers" of regular coffee (10 floz)</li>
<li>~1.3 L soft drink (these can vary widely in content)</li>
<li>~5 cups (8 floz) of black tea or ~10 cups (8 floz) of green tea</li>
<li>~5 cans of soda (these can vary widely in content)</li>
</ul>
<p>In the <a href="http://en.wikipedia.org/wiki/European_Union" title="European Union">European Union</a>, a warning must be placed on packaging if the caffeine content of any beverage exceeds 150 mg per litre. This includes caffeine from any source (including <a href="http://en.wikipedia.org/wiki/Guarana" title="Guarana">guarana</a>, which is often found in energy drinks). In many countries, caffeine is classified as a <a href="http://en.wikipedia.org/wiki/Flavouring" title="Flavouring">flavouring</a>.</p>

<h2><a id="Metabolism_and_toxicology">Metabolism and toxicology</a></h2>
<p>Caffeine is thought to act on the <a href="http://en.wikipedia.org/wiki/Brain" title="Brain">brain</a> (and in fact, most cells of the body, since all cells have adenosine receptors) by blocking <a href="http://en.wikipedia.org/wiki/Adenosine" title="Adenosine">adenosine</a> receptors (thereby blocking a pathway that leads to the breakdown of <a href="http://en.wikipedia.org/wiki/Cyclic_adenosine_monophosphate" title="Cyclic adenosine monophosphate">cyclic adenosine monophosphate</a>, cAMP). Adenosine, when bound to receptors of nerve cells, slows down nerve cell activity; this happens, among other times, during <a href="http://en.wikipedia.org/wiki/Sleep" title="Sleep">sleep</a>. The caffeine molecule, being similar to adenosine, binds to the same receptors but doesn't cause the cells to slow down; instead, the caffeine blocks the receptors and thereby the adenosine action. The resulting increased nerve activity causes the release of the <a href="http://en.wikipedia.org/wiki/Hormone" title="Hormone">hormone</a> <a href="http://en.wikipedia.org/wiki/Epinephrine" title="Epinephrine">epinephrine</a> (adrenaline), which in turn leads to several effects such as higher heart rate, increased <a href="http://en.wikipedia.org/wiki/Blood_pressure" title="Blood pressure">blood pressure</a>, increased <a href="http://en.wikipedia.org/wiki/Blood" title="Blood">blood</a> flow to <a href="http://en.wikipedia.org/wiki/Muscle" title="Muscle">muscles</a>, decreased blood flow to the <a href="http://en.wikipedia.org/wiki/Skin" title="Skin">skin</a> and inner <a href="http://en.wikipedia.org/wiki/Organ_%28anatomy%29" title="Organ (anatomy)">organs</a>, and release of <a href="http://en.wikipedia.org/wiki/Glucose" title="Glucose">glucose</a> by the <a href="http://en.wikipedia.org/wiki/Liver" title="Liver">liver</a>. In addition, caffeine, similar to <a href="http://en.wikipedia.org/wiki/Amfetamine" title="Amfetamine">amphetamines</a>, increases the levels of the <a href="http://en.wikipedia.org/wiki/Neurotransmitter" title="Neurotransmitter">neurotransmitter</a> <a href="http://en.wikipedia.org/wiki/Dopamine" title="Dopamine">dopamine</a> in the brain.</p>
<p>Caffeine is quickly and completely removed from the brain and, unlike other <a href="http://en.wikipedia.org/wiki/Central_nervous_system" title="Central nervous system">CNS</a> <a href="http://en.wikipedia.org/wiki/Stimulant" title="Stimulant">stimulants</a> or <a href="http://en.wikipedia.org/wiki/Alcohol" title="Alcohol">alcohol</a>, its effects are short lived. In many people, caffeine does not negatively affect concentration or higher mental functions, and hence caffeinated drinks are often consumed in the course of work.</p>
<p>In the <a href="http://en.wikipedia.org/wiki/Liver" title="Liver">liver</a>, the first <a href="http://en.wikipedia.org/wiki/Metabolism" title="Metabolism">metabolic</a> products of caffeine are three <a href="http://en.wikipedia.org/wiki/Xanthine" title="Xanthine">dimethylxanthines</a>: <a href="http://en.wikipedia.org/wiki/Theophylline" title="Theophylline">theophylline</a> (4%), <a href="http://en.wikipedia.org/wiki/Theobromine" title="Theobromine">theobromine</a> (12%) and paraxanthine (84%). <a href="http://en.wikipedia.org/wiki/Theophylline" title="Theophylline">Theophylline</a> relaxes <a href="http://en.wikipedia.org/wiki/Smooth_muscle" title="Smooth muscle">smooth muscles</a> of the <a href="http://en.wikipedia.org/wiki/Bronchus" title="Bronchus">bronchii</a> and has been used as a treatment of <a href="http://en.wikipedia.org/wiki/Asthma" title="Asthma">asthma</a>. <a href="http://en.wikipedia.org/wiki/Theobromine" title="Theobromine">Theobromine</a>, the principal alkaloid in <a href="http://en.wikipedia.org/wiki/Cocoa" title="Cocoa">cocoa</a> (<a href="http://en.wikipedia.org/wiki/Chocolate" title="Chocolate">chocolate</a>) can increase <a href="http://en.wikipedia.org/wiki/Blood_vessel" title="Blood vessel">blood vessel</a> dilation and <a href="http://en.wikipedia.org/wiki/Urine" title="Urine">urine</a> volume. Paraxanthine increases <a href="http://en.wikipedia.org/wiki/Lipolysis" title="Lipolysis">lipolysis</a>, leading to elevated <a href="http://en.wikipedia.org/wiki/Glycerol" title="Glycerol">glycerol</a> and free <a href="http://en.wikipedia.org/wiki/Fatty_acid" title="Fatty acid">fatty acid</a> in the <a href="http://en.wikipedia.org/wiki/Blood_plasma" title="Blood plasma">blood plasma</a>.</p>
<p>Continued consumption of caffeine can lead to tolerance. Upon withdrawal, the body becomes oversensitive to <a href="http://en.wikipedia.org/wiki/Adenosine" title="Adenosine">adenosine</a>, causing the blood pressure to drop dramatically, leading to headache and other symptoms. Any accumulated <a href="http://en.wikipedia.org/wiki/Sleep_debt" title="Sleep debt">sleep debt</a> will be fully felt on withdrawal as well.</p>
<p>Too much caffeine can lead to caffeine intoxication. The symptoms of this disorder are restlessness, nervousness, excitement, <a href="http://en.wikipedia.org/wiki/Insomnia" title="Insomnia">insomnia</a>, flushed face, <a href="http://en.wikipedia.org/wiki/Diuresis" title="Diuresis">diuresis</a>, <a href="http://en.wikipedia.org/wiki/Gastroenterology" title="Gastroenterology">gastrointestinal</a> complaints, even hallucinations. They can occur in some people after as little as 250 mg per day. More than 1,000 mg per day may result in muscle twitching, rambling flow of <a href="http://en.wikipedia.org/wiki/Thought" title="Thought">thought</a> and <a href="http://en.wikipedia.org/wiki/Speech" title="Speech">speech</a>, <a href="http://en.wikipedia.org/wiki/Cardiac_arrhythmia" title="Cardiac arrhythmia">cardiac arrhythmia</a> or <a href="http://en.wikipedia.org/wiki/Tachycardia" title="Tachycardia">tachycardia</a>, and <a href="http://en.wikipedia.org/wiki/Psychomotor_agitation" title="Psychomotor agitation">psychomotor agitation</a>. Caffeine intoxication can lead to symptoms similar to <a href="http://en.wikipedia.org/wiki/Panic_disorder" title="Panic disorder">panic disorder</a> and <a href="http://en.wikipedia.org/wiki/Generalized_anxiety_disorder" title="Generalized anxiety disorder">generalized anxiety disorder</a>.</p>
<p>The minimum lethal dose ever reported was 3,200 mg, intravenously. The <a href="http://en.wikipedia.org/wiki/LD50" title="LD50">LD</a><sub>50</sub> of caffeine (that is the lethal dosage reported to kill 50% of the population) is estimated between 13-19 grams for oral administration for an average adult. The LD<sub>50</sub> of caffeine is dependent on weight and estimated to be about 150-200 mg per kg of body mass, roughly 140-180 cups of coffee for an average adult taken within a limited timeframe that is dependent on <a href="http://en.wikipedia.org/wiki/Half-life#Half-life_in_chemistry" title="Half-life">half life</a>. The half-life or time it takes to <a href="http://en.wikipedia.org/wiki/Metabolize" title="Metabolize">metabolize</a> 50% of the caffeine, ranges from 3.5 to 100 hours. In adults the half-life is generally around 5 hours. However contraceptive pills increase this to around 12 hours and for women over 3 months pregnant it varies from 10 to 18 hours. In infants and young children the half-life may be longer than adults. With common coffee and a very rare half-life of 100 hours it would require 3 cups of coffee every hour for 100 hours just to reach LD<sub>50</sub>. Though achieving lethal dose with coffee would be exceptionally difficult, there have been many reported deaths from intentional overdosing on caffeine pills.</p>
<p>While safe for humans, caffeine and its related compounds <a href="http://en.wikipedia.org/wiki/Theobromine" title="Theobromine">theobromine</a> and <a href="http://en.wikipedia.org/wiki/Theophylline" title="Theophylline">theophylline</a> are considerably more toxic to some other animals such as dogs, horses and parrots due to a much poorer ability to metabolize these compounds.</p>
<p>Intake of caffeine can up to halve a patient's risk of <a href="http://en.wikipedia.org/wiki/Diabetes_mellitus" title="Diabetes mellitus">diabetes mellitus</a> type 2. While this was originally noticed in patients who consumed high amounts (7 cups a day), the relationship has now been shown to be linear (Salazar-Martinez 2004).</p>
<p>Intravenous caffeine (in the form of caffeine benzoate 500 mg over 1 hour) is occasionally used medically to treat post-<a href="http://en.wikipedia.org/wiki/Lumbar_puncture" title="Lumbar puncture">lumbar puncture</a> ("spinal tap") headache<a href="http://www.emedicine.com/neuro/topic557.htm" class='external autonumber' title="http://www.emedicine.com/neuro/topic557.htm">[3]</a>.</p>
<p>Although caffeine solutions are often used as a chemical standard for <a href="http://en.wikipedia.org/wiki/Basic_taste" title="Basic taste">bitterness</a>, caffeine is added to some <a href="http://en.wikipedia.org/wiki/Soft_drink" title="Soft drink">soft drinks</a> such as <a href="http://en.wikipedia.org/wiki/Cola" title="Cola">colas</a>, <a href="http://en.wikipedia.org/wiki/Irn-Bru" title="Irn-Bru">Irn-Bru</a> and <a href="http://en.wikipedia.org/wiki/Mountain_Dew" title="Mountain Dew">Mountain Dew</a> ostensibly for its taste.</p>

<h2><a id="Abuse_and_overdose">Abuse and overdose</a></h2>
<p>Caffeine, in its many forms, has been used for its stimulating effects. In modern times, though, the substance can be produced in much higher quantities, and has found its way into many products. Purer forms, such as those in caffeine <a href="http://en.wikipedia.org/wiki/Tablet" title="Tablet">pills</a>, are easily available. These pills are sometimes used by college students and <a href="http://en.wikipedia.org/wiki/Shift" title="Shift">shift</a> workers to last an entire night without sleep.</p>
<p>Caffeine pills have been under media fire for recent and past deaths of students, usually take on the form of a caffeine <a href="http://en.wikipedia.org/wiki/Overdose" title="Overdose">overdose</a>. One such example of this was the death of a <a href="http://en.wikipedia.org/wiki/North_Carolina" title="North Carolina">North Carolina</a> student, Jason Allen. He swallowed most of a bottle of 90 such pills <a href="http://www.collegepublisher.com/media/paper87/DFPArchive/science/1103981.html" class='external autonumber' title="http://www.collegepublisher.com/media/paper87/DFPArchive/science/1103981.html">[4]</a>. This was the equivalent of about 250 cups of <a href="http://en.wikipedia.org/wiki/Coffee" title="Coffee">coffee</a> (or, alternatively, a gallon and a half (5 liters) of <a href="http://en.wikipedia.org/wiki/Espresso" title="Espresso">espresso</a>, or 22 gallons (~85 liters) of <a href="http://en.wikipedia.org/wiki/Mountain_Dew" title="Mountain Dew">Mountain Dew</a>, though the soft drink is not caffeinated in all areas). Allen probably ingested about 18 grams of caffeine, since caffeine pills are restricted to 200 milligrams or less in the U.S., and most manufacturers make them in that size. A few other deaths by caffeine overdose have been known, almost always in the case of massive pill consumption.</p>
<p>Studies in humans have shown that caffeine may cause miscarriage or may slow the growth of a developing fetus when given in doses greater than 300 mg (an amount equal to three cups of coffee) a day. In addition, use of large amounts of caffeine by the mother during pregnancy may cause problems with the heart rhythm of the fetus.</p>
<p>Excessive ingestion of caffeine can result in <a href="http://en.wikipedia.org/wiki/Hypertension" title="Hypertension">increased blood pressure</a> and <a href="http://en.wikipedia.org/wiki/Tachycardia" title="Tachycardia">pulse</a>, increased <a href="http://en.wikipedia.org/wiki/Diuresis" title="Diuresis">urine production</a>, <a href="http://en.wikipedia.org/wiki/Vasoconstriction" title="Vasoconstriction">vasoconstriction</a> (tightening or constricting of superficial blood vessels) sometimes resulting in cold hands or fingers, increased amounts of <a href="http://en.wikipedia.org/wiki/Fatty_acid" title="Fatty acid">fatty acids</a> in the blood, and increased production of <a href="http://en.wikipedia.org/wiki/Gastric_acid" title="Gastric acid">gastric acid</a>.</p>
<p>Those suffering from overdose should find a quiet place to rest. Within an hour after the effects first arise, peak influence on the body should occur, with a 15-30 minute plateau, after which the effects should abate and the sufferer can return to normal activity.</p>
<p>Long periods of abuse can lead to detrimental effects on the esophagus (persons who consume high amounts of caffeine may have a risk for higher incidents of <a href="http://en.wikipedia.org/wiki/Peptic_ulcer" title="Peptic ulcer">peptic ulcers</a>, erosive <a href="http://en.wikipedia.org/wiki/Esophagitis" title="Esophagitis">esophagitis</a>, and <a href="http://en.wikipedia.org/wiki/Gastroesophageal_reflux_disease" title="Gastroesophageal reflux disease">gastroesophageal reflux disease</a>), heart problems, <a href="http://en.wikipedia.org/wiki/Insomnia" title="Insomnia">insomnia</a>, chronic muscle tension and nervousness.</p>
<p>One dangerous form of caffeine use is to stay alert when one is under the influence of alcohol or in severe <a href="http://en.wikipedia.org/wiki/Sleep_debt" title="Sleep debt">sleep debt</a>. This tricks users into thinking they are more alert than they really are. Taking part in certain activities, such as <a href="http://en.wikipedia.org/wiki/Driving" title="Driving">driving</a>, may be dangerous in such cases. Even aside from such activities, caffeine does not make up for the poor mental performance caused by lack of sleep.</p>
<p>The term <a href="http://en.wikipedia.org/wiki/Caffeinism" title="Caffeinism">caffeinism</a> has been coined to mean <a href="http://en.wikipedia.org/wiki/Addiction" title="Addiction">addiction</a> to (or debilitating dependence on) caffeine.</p>

<h2><a id="History">History</a></h2>
<p>Although <a href="http://en.wikipedia.org/wiki/Tea" title="Tea">tea</a> consumption in <a href="http://en.wikipedia.org/wiki/China" title="China">China</a> began thousands of years ago, the first documented use of caffeine in a beverage for its <a href="http://en.wikipedia.org/wiki/Pharmacology" title="Pharmacology">pharmacological</a> effect was by the <a href="http://en.wikipedia.org/wiki/Sufism" title="Sufism">sufis</a> of <a href="http://en.wikipedia.org/wiki/Yemen" title="Yemen">Yemen</a>, who used <a href="http://en.wikipedia.org/wiki/Coffee" title="Coffee">coffee</a> to stay awake during prayers in the 15th century. In the 16th century there were <a href="http://en.wikipedia.org/wiki/Coffeehouse" title="Coffeehouse">coffeehouses</a> in <a href="http://en.wikipedia.org/wiki/Cairo" title="Cairo">Cairo</a> and <a href="http://en.wikipedia.org/wiki/Mecca" title="Mecca">Mecca</a>. Coffeehouses opened in Europe in the 17th century.</p>
<p>Caffeine was isolated by the <a href="http://en.wikipedia.org/wiki/Germany" title="Germany">German</a> chemist <a href="http://en.wikipedia.org/wiki/Friedrich_Ferdinand_Runge" title="Friedrich Ferdinand Runge">Friedrich Ferdinand Runge</a> in <a href="http://en.wikipedia.org/wiki/1819" title="1819">1819</a>. According to the legend, he did this at the instigation of <a href="http://en.wikipedia.org/wiki/Johann_Wolfgang_von_Goethe" title="Johann Wolfgang von Goethe">Johann Wolfgang von Goethe</a> (Weinberg &amp; Bealer 2001).</p>
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